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        // 4. 写一个函数，能翻转传入的任意数组，并把翻转结果通过返回值返回。
		function turn(arr){
			var arr1 =[]
			for(var i = arr.length -1 ; i >= 0 ; i --){
				arr1[arr1.length] = arr[i];
			}
			return arr1;
			}	
		var a = [1,2,3,4,5,6,7,8,9];
		console.log(turn(a));
	</script>
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